This invention generally relates to apparatuses and methods for treating water and other fluids, including, but not limited to, agricultural and industrial waste water, utilizing a combination of screening and a benign, naturally occurring, biological processes to eliminate and cut the production of, often associated, offensive odors.
For purposes of this patent, the following terms are defined. As used herein, the term xe2x80x9cconveyedxe2x80x9d or xe2x80x9cconveyxe2x80x9d means and refers to any system or process for directing, channeling, sending, spraying, blowing, moving, funneling, pouring, pumping wastewater or other solid or at partially liquid material. As used herein, the term xe2x80x9ctankxe2x80x9d means and refers to a bin(s), pond(s), container, area, and the like. As used herein, the term xe2x80x9ctrolleyxe2x80x9d means and refers to a bin, tank, collection site, collection vehicle, area, pile, and the like. As used herein, the term xe2x80x9cpass,xe2x80x9d xe2x80x9cpassing,xe2x80x9d xe2x80x9cpassed,xe2x80x9d and other conjugations means and refers to convey, to direct and/or to transport via any method or structure common in the art such as pipe, funnel, trough, line, slope, gully, trench, river, stream, and the like. As used herein, the term xe2x80x9clagoonxe2x80x9d means and refers to a lagoon, pond, lake, stream, retention structure, facultative pond and the like.
When wild hogs roamed the forest in sparse numbers with the population determined by the available food sources, the environmental impact of the hog excretion was insignificant. The individual animal roamed freely, spreading his waste over large areas as he traveled. Later, when man domesticated hog and other livestock, and increased the local concentration to correspond to the caretakers food production, the environmental impact of waste was at first minimal. The farmer removed the waste manure from the pig-sty and spread it over his farm for fertilizer. In recent times, however, livestock production density has dramatically increased. For example, the specialty hog production operators purchased their hog feed (cereal grains) from other farmers who specialized in the production of grain cereal. This enables one operator to have the hog production facility of 10,000 head of hogs or more. The production of hog manure now becomes a problem. The spreading of large quantities of hog manure on land requires an extensive amount of land. The soil has a finite capacity to degrade animal feces, and when exceeded it becomes the equivalent of a pile of manure. The waste is often accumulated and dispersed over the cropland at specific times of the year. However, there are physical limitations on the distribution of the waste because it cannot be practically applied to near mature crops without the destruction of the crop. Also it cannot be applied when the waste may run off the soil because the soil is saturated or frozen. In fact, several states within the U.S. have created regulations prohibiting land application during the winter months.
In addition to the practical limits of the distribution of animal feces, regulatory agencies have applied limits on the amount of feces that may be spread. The regulations limit the amount of animal feces per acre to be about equivalent to the plant uptake of the non-biodegradable components. These regulations were created to prohibit the surface run-off from storm water and the excess percolation of the soluble waste components into the ground water.
In recent times, livestock producers have elected to create pits or lagoons for the collection of the waste. In the barns or houses, the animals live on elevated flooring which permits the feces to drop through the floor to a sub-floor. This sub-floor is periodically flushed to remove the feces and maintain a healthy living environment. The feces, with the wash down water as a vehicle, flow to the storage lagoon. The water utilized to flush the livestock production floor and move the freshly produced feces to the lagoon is usually recycled supernatant from the storage lagoon. Recycling the wastewater provides two advantages to the producer. First, it reduces that amount of fresh water that must be provided and secondly, since it is recycled from the storage lagoon, the size of the storage facility can be significantly reduced.
The problem with the recycled water is that it contains high levels of ammonia (breakdown product of the waste urea) and odors, which are not beneficial to the health of the livestock. High levels of ammonia in the flush water require the building to be vented to reduce the ambient levels of ammonia. Increased ventilation lowers the ambient temperatures in the winter. The lower temperatures lower the rate of weight gain of the animals and increases the food requirement of the animal to maintain body temperature.
Biological cultures purify water by exploiting the metabolic processes of various bacterial and algal species to convert organic and inorganic waste products into benign end products, typically carbon dioxide and a reproduction of the species. However, intermediate products formed by biological processes can include methane and sulfur containing gases, volatile organic acids or other volatile or odiferous products, depending on the nature of the culture, the waste being digested and the ambient environment.
Biological cultures can be fostered of desirable microorganisms, which provide the functional basis for the wastewater treatment by metabolically converting the waste products. However, cultures of undesirable microorganisms which produce undesirable tastes, odors, growths, or which are actually toxic are also possible. Therefore, it is important in biological wastewater treatment that cultures of suitable microorganisms are fostered and the undesirable cultures avoided.
The organic material in the wastewater serves both as an energy source and a source of carbon for cell synthesis by the microorganisms of the culture. Microorganisms are both reactants and products in the biological treatment of wastewater. Typical configurations of biological reactor cultures for purifying water include suspended culture processes and attached growth systems such as fixed-film reactors. Suspended cultures include activated sludge (flocculent cultures), aerated lagoons, oxidation ponds, and anaerobic cultures.
The oxygen level present in the culture material affects biological digestion of organic waste material because the oxygen level determines the metabolic pathway available to the microorganism. Aerobic conditions provide plenty of oxygen to the culture, and foster the growth of microorganisms that can use the exogenous oxygen as a terminal electron acceptor in the oxidation of organic acids generated form the metabolic breakdown of organic material, i.e. aerobic biological activity. If insufficient exogenous oxygen is available to the culture, the conditions are anaerobic. Under anaerobic conditions, the absence of oxygen as a terminal electron acceptor results in the excretion of organic acids into the culture medium as waste.
Farmers often create storage lagoons on their farms to accumulate and store the flushed wastewater, feces and urine until an appropriate time to distribute the wastes over the land. The surface water is utilized as flush water not only to reduce the amount of water consumed by the animal production, but also to conserve the capacity of the lagoon. Using the lagoon water for flushing reduces the water consumption by 70-90% and proportionally reduces the required size of the lagoon. The wastewater is usually stored until planting time and applied to cropland in place of a commercial fertilizer.
Currently, during the storage process, due to the large volume of animal waste entering the lagoon, there is insufficient oxygen present to support the growth of aerobic cultures and/or aerobic biological activity. In the absence of the desired oxygen, the microbial growth in the lagoon converts to anaerobic activity. This anaerobic activity leads to what is commonly known as a xe2x80x9csepticxe2x80x9d lagoon. In a septic lagoon a very foul odor is present from the production of hydrogen sulfide, organic-sulfide compounds, organic acids, and etc. When the accumulated waste liquid is distributed over the cropland by spray irrigation, the foul smelling volatile gases are liberated, producing a very undesirable environment.
Aeration equipment can be installed to provide sufficient dissolved oxygen to maintain an aerobic culture. However, the energy cost to operate the aerobic treatment is very cost prohibitive. There are several methods of aeration available. Surface aerators are commonly used in large open areas. The surface aerator consists of an electric motor driven impeller suspended in the throat of a venturi with the entire unit mounted on a float to suspend the impeller just below the surface. As the impeller spins, it pumps the water up forming a large circular spray. Oxygen is dissolved in the water as it falls through the air. The amount of water spray and subsequently the amount of oxygen dissolved is directly proportioned to the amount of water pumped and therefore the horsepower of the motor and energy consumed.
Another commonly used method to increase the dissolved oxygen content of the lagoon is to blow air thorough an aeration system located on the bottom of the pond. The air is forced through a device with small openings to create small bubbles. As the bubbles rise through the liquid, oxygen is dissolved in the water. Again the amount of oxygen dissolved is directly proportional to the amount of air forced into the basin and therefore the horsepower utilized and energy consumed.
With these methods, it is possible to provide enough energy to supply sufficient oxygen to maintain an aerobic culture, but such methods are not entirely practical. The average waste generated by swine production is 3.1 pounds of BOD and 8.4 pounds of COD per day per 1000 pounds of live stock. This amount would be very cost prohibitive with the prior art methods.
Other methods that have developed in thart concentrate on screening the undissolved particles from the waste water prior to flushing. Typically, the flush water will consist of both dissolved ingredients and suspended undissolved solids or particles (undissolved ingredients). These undissolved particles are of varying size from sub-micron to much larger visible particles.
There are a variety of screen separators being used in the art field for such screening. However, the screens only remove about 15-20% of the organic mass. These large particles that can be screened are insignificant in the treatment process because removing only 20% of the organic mass will only reduce the energy consumption by 20%. Various types of screenxe2x80x94gravity inclined screen, inclined screens with roll compactor, rotating screens, screens with drag chains, have been utilized with either wedge wire construction or perforated metal construction and types produce essentially the same results in that most of the particles are too small to be removed by screen-separating devices. In any case, the majority of the fecal matter is unscreened and left to produce the foul smell and septic environment as heretofore described.
The foul odors of waste water become apparent in most operations, including, but not limited to:
(a) When the stored water is returned to the barns as flush water, odors are liberated;
(b) Spray operations: when the wastewater is applied to the cropland by spray irrigation (most common method), the liquid is pumped under high pressure through a nozzle and sprayed over large area. The spray area as well as all areas downwind has a putrid odor and is very undesirable;
(c) Winter thermal changeover: In the winter to spring of the year, the normal thermo dine of the lagoon is disturbed. Due to the temperature differences the bottom layers roll to the surface, creating an extra heavy liberation of noxious odors; and,
(d) the like.
Over the past few decades, more people have found it desirable to live in a country atmosphere rather then the conventional city life resulting in a greater number of people living near agricultural centers. The foul odor emanating from the anaerobic lagoons and spray fields has increasingly become a major area environmental issue. For example, the state of North Carolina has recently passed a moratorium prohibiting the creation of any new anaerobic lagoons. In fact, new rules are being created to phase out the use of all anaerobic lagoons because of the environmental and social problems. Other areas have proposed methods for the treatment of agricultural wastewater using biological techniques, the problem of odor and the economical removal of the source of the odor has not been addressed.
A few relevant prior art patents are as follows:
U.S. Pat. No. 5,545,325 discloses a facility for combined aerobic and anaerobic treatment of livestock wastewater disclosure. This is accomplished with a natural solid-liquid separation device comprising a digester with an automatic skimmer installed at the upper part of the digester, and a level sensing control valve to control the volume of wastewater in the digester;
U.S. Pat. No. 5,480,548 discloses a wastewater purification process is disclosed including directing the wastewater through at least one aerobic zone and at least one anaerobic zone in repeating or alternating segments. A portion of effluent from the one or more anoxic zones are fed through at least one aerobic zone to which wastewater is fed and returned to the upstream portion of the anoxic zone;
U.S. Pat. No. 5,472,472 discloses a process for the bioconversion of soluble and suspended organics from animal waste wherein the wastewater is treated through a series of ecoreactors and bioreactors, including aerobic and anaerobic treatment. Soluble phosphorus is precipitated with metallic salts;
U.S. Pat. No. 4,824,563 discloses a method of treating high concentration organic wastewater in dependence upon microorganisms. The method includes an anaerobic operation tank, an aerobic tank and an ozone treatment tank;
U.S. Pat. No. 4,999,111 discloses a process for treating wastewater including aerobic, anaearobic, and anoxic treatment. The process of the ""111 patent includes splitting the stream of wastewater into a main stream and a side stream wherein the anoxic treatment takes place in the side stream. Activated sludge is generated in the side stream and is recycled to the mainstream treatment process that includes at least one aerobic treatment zone.
The present invention generally relates to processes and apparatuses for treatment of waste water.
This summary is not intended to be a limitation with respect to the features of the invention as claimed and any examples are merely intended as embodiments, and the scope and other objects can be more readily observed and understood in the detailed description of the preferred embodiment and the claims.